Directional drilling (also referred to in the art as “horizontal drilling” or “horizontal directional drilling”) was invented in the 1920s and the technology was originally used in oil fields to increase oil production. In the 1990s, directional drilling technology was adapted for utility installations. Directional bores have been installed for pipelines carrying oil, natural gas, petrochemicals, water, sewage, and other products. Also, directionally drilled holes have been used to install conduits which carry electric and fiber optic cables. Such continuous pipes, conduits, casings and the like are referred to hereinafter generally as “pipe”.
Besides crossing under highways, railroads, airport runways, shore approaches, traffic islands, and areas congested with buildings; directionally drilled installations have been made under rivers and waterways, pipeline corridors, and protected wetlands. Directional borings have the least environmental impact of any alternate construction method. Directional drilling technology also allows placement of pipe under obstacles, provides maximum protection for the installation, and minimizes maintenance costs. During installation, normal business operations are usually not interrupted. Directional borings also have a predictable and short construction schedule.
Typically, after a directional boring pass is complete, a permanent pipe (e.g. a gas pipe, conduit, or casing of some sort) is pulled or pushed through the boring also known as a borehole. In the prior art, the pipe, which may be formed of, for example, metal or plastic, is not necessarily provided with exterior chafe protection prior to being inserted into the boring and thus, the pipe and any pipe coatings are vulnerable to damage from contact with protruding rocks and the like.
Many utility distribution piping and cable systems are buried underground throughout the world. Older piping systems were often formed of cast iron or bare steel pipe. Newer systems may include coated steel or polyethylene. Older systems may also tend to be in urban or congested areas under asphalt or concrete paving that would render the replacing or rehabilitating such pipes expensive and disruptive to surface activities. Sliplining or host pipe insertion has also been used as a method for rehabilitation of existing pipelines to repair leaks or restore structural stability. Sliplining is completed by installing a smaller, “carrier pipe” into a larger “host pipe.” The carrier pipe may be continuous along an entire run of pipeline or consist of multiple segments of pipe that are joined or fused end to end. Common material used to slipline an existing pipe include medium and high density polyethylene (HDPE), fiberglass reinforced pipe and poly vinyl chloride (PVC). A host pipe may include debris, slag, burrs or sharp internal edges between pipe segments, as well as internal projections or coupons at service connection fittings that may damage or score the external surface of the carrier pipe as it is inserted within the host pipe.
As described in CA Patent No. 2517980C, hoses have been used as protective sleeves for borehole pipe installation. However, such relatively flexible materials, such as fire hoses, polyester materials, and other relatively loose weave materials, are water absorbent and can be difficult to install once water logged. Also, post-installation ingress of water and other ground contaminants such as petrochemicals cause pipe corrosion and/or degradation and in some cases ultimately pipe failure. Such pre-formed hoses can be difficult and time consuming to pull over pipes being prepared into pipe-hose assemblies for installation into the borehole. Post-installation, such hoses can be subject to undesirable permanent bonding between the pipe, the hose, and the surrounding soil matrix.
A coupler may be used to hold a protective sleeve on a pipe during insertion of the pipe-protective sleeve assembly. A coupler may also be used to hold an electrical tracer wire which can be installed into the borehole along with the pipe-protective sleeve assembly. Unfortunately, some physical damage to the protective sleeve and/or the tracer wire is common.
There is a need for a coupler method and apparatus to substantially eliminate damage to the protective sleeve and tracer wire at or near a coupler during insertion into a borehole and to protect carrier pipe during host pipe insertion or sliplining.